Conventionally, there has been known a receiver that receives a high-frequency signal and frequency-converts the received signal to a baseband signal. Such a receiver is disclosed, for example, in NPL 1. FIG. 1 is a block diagram of receiver 500 of NPL 1.
In FIG. 1, receiver 500 is provided with antennas 1-1 and 1-2, low noise amplifiers (hereinafter, referred to as “LNA”) 2-1 and 2-2, phase adjusters 3-1 and 3-2, frequency converters 4-1 and 4-2, and local oscillation signal generating section 5.
Received signal received by antennas 1-1 and 1-2 are amplified by LNAs 2-1 and 2-2 and outputted to phase adjusters 3-1 and 3-2. Phase adjusters 3-1 and 3-2 perform phase adjustment so that the received signals amplified by LNAs 2-1 and 2-2 respectively become in-phase with each other. Phase adjusters 3-1 and 3-2 output the phase-adjusted received signals to frequency converters 4-1 and 4-2. Local oscillation signal generating section 5 outputs a local oscillation signal which is a high-frequency signal close to the received signal to frequency converters 4-1 and 4-2. Frequency converters 4-1 and 4-2 frequency-convert the phase-adjusted received signals using the local oscillation signal and output the converted signals as baseband signals.
Thus, receiver 500 maximizes an amplitude gain by combining the received signals controlled so as to be in-phase with each other. That is, receiver 500 constitutes a diversity receiver that performs so-called maximum ratio combining and improves reception sensitivity.
FIG. 2 is a configuration diagram of phase adjusters 3-1 and 3-2 shown in FIG. 1. A signal inputted from a Vin terminal is amplified by transistors M1 and 2. The signal amplified by transistor M1 passes through resistor R1. At this time, a phase change occurs, which is determined by resistor R1 and capacitor C1. Similarly, when the signal amplified by transistor M2 passes through capacitor C2, a phase change occurs, which is determined by capacitor C2 and resistor R2. The phase-changed signals are combined in a common load Z and outputted from a Vout terminal. At this time, phase adjusters 3-1 and 3-2 cause a difference between a phase change determined by resistor R1 and capacitor C1 and a phase change determined by capacitor C2 and resistor R2 to become 90 degrees and make the amounts of amplification of transistors M1 and M2 variable to thereby perform phase adjustment.